Replaced is_null() with is_valid in SurfaceId and related classes.

cc/layers/surface_layer.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/surface_layer.h"
 
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 39 matching lines @@
 }
 
 SurfaceLayer::SurfaceLayer(const SatisfyCallback& satisfy_callback,
                            const RequireCallback& require_callback)
     : surface_scale_(1.f),
       satisfy_callback_(satisfy_callback),
       require_callback_(require_callback) {}
 
 SurfaceLayer::~SurfaceLayer() {
   DCHECK(!layer_tree_host());
-  DCHECK(destroy_sequence_.is_null());
+  DCHECK(!destroy_sequence_.is_valid());
 }
 
 void SurfaceLayer::SetSurfaceId(const SurfaceId& surface_id,
                                 float scale,
                                 const gfx::Size& size) {
   SatisfyDestroySequence();
   surface_id_ = surface_id;
   surface_size_ = size;
   surface_scale_ = scale;
   CreateNewDestroySequence();
 
   UpdateDrawsContent(HasDrawableContent());
   SetNeedsPushProperties();
 }
 
 std::unique_ptr<LayerImpl> SurfaceLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return SurfaceLayerImpl::Create(tree_impl, id());
 }
 
 bool SurfaceLayer::HasDrawableContent() const {
-  return !surface_id_.is_null() && Layer::HasDrawableContent();
+  return surface_id_.is_valid() && Layer::HasDrawableContent();
 }
 
 void SurfaceLayer::SetLayerTreeHost(LayerTreeHost* host) {
   if (layer_tree_host() == host) {
     Layer::SetLayerTreeHost(host);
     return;
   }
 
   SatisfyDestroySequence();
   Layer::SetLayerTreeHost(host);
   CreateNewDestroySequence();
 }
 
 void SurfaceLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
   TRACE_EVENT0("cc", "SurfaceLayer::PushPropertiesTo");
   SurfaceLayerImpl* layer_impl = static_cast<SurfaceLayerImpl*>(layer);
 
   layer_impl->SetSurfaceId(surface_id_);
   layer_impl->SetSurfaceSize(surface_size_);
   layer_impl->SetSurfaceScale(surface_scale_);
 }
 
 void SurfaceLayer::CreateNewDestroySequence() {
-  DCHECK(destroy_sequence_.is_null());
+  DCHECK(!destroy_sequence_.is_valid());
   if (layer_tree_host()) {
     destroy_sequence_ = layer_tree_host()
                             ->GetSurfaceSequenceGenerator()
                             ->CreateSurfaceSequence();
     require_callback_.Run(surface_id_, destroy_sequence_);
   }
 }
 
 void SurfaceLayer::SatisfyDestroySequence() {
   if (!layer_tree_host())
     return;
-  DCHECK(!destroy_sequence_.is_null());
+  // Sometime frame_sink_id_ is null

[piman, 2016/11/08 23:16:34]

What does this comment refer to? There's no frame_sink_id_ here. Is it in
reference to destroy_sequence_.frame_sink_id?

With your change, doesn't that mean the DCHECK is incorrect?

[Alex Z., 2016/11/09 15:29:15]

Sorry about the confusion.
That was one of the notes I left while debugging. It must have somehow escaped
the sweep when I removed my debug statements.
I will remove it in the next patchset.

+  DCHECK(destroy_sequence_.is_valid());
   std::unique_ptr<SatisfySwapPromise> satisfy(
       new SatisfySwapPromise(destroy_sequence_, satisfy_callback_));
   layer_tree_host()->GetSwapPromiseManager()->QueueSwapPromise(
       std::move(satisfy));
   destroy_sequence_ = SurfaceSequence();
 }
 
 }  // namespace cc